I. Field of the Invention
This invention relates to sleeve holders for optical connectors of so-called plug-in type mounted to. devices by plug-in connection.
II. Description of the Prior Art
The conventional sleeve holder for the optical connector "a", as shown in FIG. 4(A), comprises, a tube-shaped main body "e" in which two engaging flanges "b" and "c" having a predetermined interval "1" in an axis direction with each other are provided in a protruding manner on an outer circumference of one-end of the tube-shaped main body "e", a tube body "f" which fits coaxially on the one-end of the main body "e", and a split sleeve "g" which is mounted on an inside of the tube body "f".
Symbols "h" and "i" depict engaging protrusions provided on an inside surface of an opening between the main body "e" and the tube body "f", thereby the split sleeve "g" is prevented from being disconnected from the sleeve holder "a".
In the optical connector incorporated with the sleeve holder "a" in FIG. 5, the sleeve holder "a" provided therein with the split sleeve "g" is inserted and held at a tip end of a PA housing "j" (housing on a package-side) fixed on the package, while a plug "m" provided with a ferrule "k" forced from its backside end by a spring "n" is inserted into the PA housing "j" from the rear-side, and the ferrule "k" is inserted and held in the split sleeve "g" within the sleeve holder "a".
A holding mechanism by the PA housing "j" and the sleeve holder "a" is as shown by two point chain lines fin FIG. 4 in that engaging pieces "p" protruding on the inside surface on the tip end of the PA housing "j" are separated upper and lower respectively against their sleeve forces, and after the spring holder "a" is inserted, the engaging pieces "p" are inserted and held between the engaging flanges "b" and "c" of the sleeve holder "a" by restoring forces of the engaging pieces "p".
A pressing force of the spring "n" (for example, 7.8N to 11.8N, in accordance with JIS (JAPANESE INDUSTRIAL STANDARDS) C 5971, Item 6, No. 7) is set so that such force is not applied to the PA housing "j" but is greater than the ferrule holding force (for example, 2.9N to 6.9N, in accordance with JIS C 5971, Item 6, No. 6) of the split sleeve "g".
By this setting, the sleeve "g" of the ferrule "k" comes to have a length of L.sub.1 (for simplification of the explanation, this includes a length "1" of the edge inside the opening) as shown in FIG. 5(A) when the ferrule "k" is inserted into the split sleeve "g".
The ferrule holding force of the split sleeve "g" is lower than the ferrule pressing force due to the spring "n" of the plug "m", accordingly even if a ferrule "K'" incorporated in the other plug "m'" in FIG. 5(A) is inserted into a position in FIG. 5(B) from the other-side end of the sleeve holder "a", then in this stage, positions of the sleeve holder "a", split sleeve "g", and ferrule "k" are not varied, the condition in FIG. 5(A) therefore remains as it is.
When a sufficient pressing force is generated between the ferrules by pressing the other-side plug "m'" and by butting the ferrules against each other, that is, when setting it to an optical reference position, in other words when the ferrule "k'" is inserted onto the position shown in FIG. 5(C), then the ferrule "k" moves back by "1.sub.2 " relative to the split sleeve "g" because the sleeve holder "a" is held by the engaging piece "p" of the PA housing "j". Therefore, the sleeve "g" of the ferrule "k" comes to have a length of L.sub.1 ' (=L.sub.1 -1.sub.2) as shown in FIG. 5(C).
"1.sub.2 " and "1.sub.2 '", which are formed at a ferrule "k'"-side, depend on characteristics of the springs pressing the respective ferrules, however, those have in general the same extent of sizes.
That is, the ferrules "k" and "k'" are in contact with each other by being pressed by the springs "n" and "n'" having the same extent of resilient forces.
When the ferrule "k'" is pulled out by pulling out the other-side plug "m'" as in FIG. 5(D), then the one-side ferrule "k", which is pressed and energized forward by a resilient force of the spring "n", intends to return to the position where it existed before the other-side ferrule "k'" was inserted, or to the condition shown in FIG. 5(A).
Simultaneously, the ferrule "k" is forced back to the left by 12 in the drawing by the spring "n" against the ferrule holding force of the split sleeve. The split sleeve "g" and the sleeve holder "a" are pressed by a force corresponding to the ferrule holding force, thus, the ferrule "k" returns to the position L.sub.1 under the condition that the pressing force corresponding to the ferrule holding force just remains against to the split sleeve "g" and the sleeve holder "a" as shown in FIG. 5 (D). That is, the sleeve holder "a" comes to the condition that, by its engaging flange "c", the engaging pieces "p" of the PA housing "j" is pressed by a force corresponding to the ferrule holding force or by the force of 2.9N to 6.9N according to the reference as formerly described.
As described above, in the conventional sleeve holder, once the other-side ferrule "k'" is pulled out, since the pressing force of the sleeve holder "a" acts on the engaging pieces "p" of the PA housing "j", the engaging pieces "p" are separated upper and lower each other against their resilient forces. Consequently, in the prior art the sleeve holder "a" slipped off to contact with the other-side ferrule "k'"-side, or the engaging pieces "p" were disconnected from the housing, or the engaging pieces "p" of the PA housing "j" were broken.
In the above condition, the sleeve holder or sleeve itself is semifixed on the engaging pieces "p" by the force corresponding to the ferrule holding force. Hence, when the other-side plug "m'" incorporated with the ferrule k' is inserted again, and in the case where a positional displacement from the axis is generated, a receiving port of the ferrule of the sleeve holder "a" can not follow it satisfactorily and does produce galling or the like, this therefore tends to mechanically break the sleeve "g".
In particular, such trouble comes great when it is applied to a multi-centered construction.
The present invention has been made for solving the problem in the prior art. An object of the invention is to provide a sleeve holder for an optical connector capable of facilitating the plug insertion, preventing slip-off of a sleeve holder, the increase of a required insertion force, and breaking of a split sleeve, and making it durable for its repeated use in a long time period, by way that a condition where a pressing force of the sleeve holder always does not act on the engaging pieces of the PA housing is kept even in repeating a predetermined operation through insertion or pull-out of a plug.